# Find First Non-Repeating Character in a String

Find first non-repeating character in a string

Given an input string, Write a code to find first Non-repeating character in a string. Suppose an input string is webrewrite, the first non-repeated character in this string is b.

In this tutorial, we will write a code in multiple programming languages to solve this problem.

## How to Find First Non-Repeating Character in a String

Method 1 – Naive Approach

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Use two for loops and compare each character with every character of a string.  But the time complexity using this approach is  O(n2).

Method 2 – Create key and value pairs for character and it’s count

We can create a key and value pairs for character and it’s count. This approach is much better as compared to first one. Let’s implement this method.

## PHP Code to Find First Non-Repeating Character in a String

Let’s try to solve this problem in a single traversal.

Method 2:

## C++ Program Find First Non-Repeating Character in a String

In this code, I am using C++ map library to make a hash (key and value pair).

## Java Program to Find First Non-repeating character in a String

### Conclusion

If you know some other efficient way to solve this problem then let us know through your comments.

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• Guest

That’s my method :
` char str[] = "ilkerburaknet"; int N = strlen(str);`

`int i,j,found = 0; char firstnonrep = NULL; for(i=0;i<N;i++){ found = 0;`

` for(j=0;j<N;j++){ if(str[i]==str[j]){ found++; } } if(found==1) { firstnonrep = str[i]; printf("%c",firstnonrep); break; } }`

• Guest

[sourcecode language=”c”]
char str[] = “ilkerburaknet”;
int N = strlen(str);

int i,j,found = 0;
char firstnonrep = NULL;
for(i=0;i<N;i++){
found = 0;

for(j=0;j<N;j++){
if(str[i]==str[j]){
found++;
}
}
if(found==1) {
firstnonrep = str[i];
printf("%c",firstnonrep);
break;
}
}
[/sourcecode]

• Guest